<?php
define("TOKEN", "akun888");
$wechatObj = new wechatCallbackapiTest();
$wechatObj->valid();
class wechatCallbackapiTest
{
public function valid()
    {
        $echoStr = $_GET["echostr"];
        if($this->checkSignature()){
        echo $echoStr;
        exit;
        }
    }
public function responseMsg()
    {
        $postStr = $GLOBALS["HTTP_RAW_POST_DATA"];
        if (!empty($postStr)){
            $postObj = simplexml_load_string($postStr, 'SimpleXMLElement', LIBXML_NOCDATA);
            $fromUsername = $postObj->FromUserName;
            $toUsername = $postObj->ToUserName;
            $keyword = trim($postObj->Content);
            $time = time();
            $textTpl = "<xml>
                        <ToUserName><![CDATA[%s]]></ToUserName>
                        <FromUserName><![CDATA[%s]]></FromUserName>
                        <CreateTime>%s</CreateTime>
                        <MsgType><![CDATA[%s]]></MsgType>
                        <Content><![CDATA[%s]]></Content>
                        <FuncFlag>0</FuncFlag>
                        </xml>";             
        if(!empty( $keyword ))
                        {
                      $msgType = "text";
                        $contentStr = "Welcome to wechat world!";
                        $resultStr = sprintf($textTpl, $fromUsername, $toUsername, $time, $msgType, $contentStr);
                        echo $resultStr;
                        }else{
                        echo "Input something...";
                        }
            }else {
            echo "";
            exit;
            }
        }
private function checkSignature()
{
    $signature = $_GET["signature"];
    $timestamp = $_GET["timestamp"];
    $nonce = $_GET["nonce"];   
    $token = TOKEN;
    $tmpArr = array($token, $timestamp, $nonce);
    sort($tmpArr);
    $tmpStr = implode( $tmpArr );
    $tmpStr = sha1( $tmpStr );
    if( $tmpStr == $signature ){
    return true;
    }else{
    return false;
    }
  }
}
?>